Ligands of the tumor necrosis factor (TNF) superfamily have important roles in normal development processes including apoptosis, regulation of immune cell functions and other cell type-specific responses. They also play a significant role in various acquired and genetic diseases, including cancer and autoimmune diseases.
The TNF ligand superfamily is characterized by a conserved extracellular C-terminal domain referred to as TNF homology domain (THD) (Bodmer, J. L. et al. (2002), TRENDS in Biochemical Sciences, 27(1):19-26). The THDs, which share a virtually identical tertiary fold and exhibit a sequence identity between family members of approx. 20 to 30%, are responsible for receptor binding and non-covalently interact to form (homo-)trimeric complexes which are then recognized by their specific receptors. Although most ligands are synthesized as membrane-bound proteins, more specifically type II (i.e., intracellular N-terminus and extracellular C-terminus) transmembrane proteins, soluble cytokines can be generated by proteolytic cleavage of the extracellular domains comprising the THD (Bodmer, J. L. et al. (2002), TRENDS in Biochemical Sciences, 27(1):19-26).
The term “interleukin (IL)” refers to a group of cytokines with complex immunomodulatory functions, including cell proliferation, maturation, migration and adhesion. Interleukins also play an important role in immune cell differentiation and activation (Brocker, C. et al. (2010), Human Genomics, 5:30-55).
It was an object of the present invention to provide multifunctional, in particular bifunctional or dual-acting, cytokine fusion proteins of ligands of the TNF superfamily and interleukins. It was a further object of the present invention to provide nucleic acid molecules, in particular RNA molecules, encoding such cytokine fusion proteins.